Autonomous cruising system, navigational sign identifying method, and non-transitory computer-readable medium

ABSTRACT

An autonomous cruising system is capable of discriminating a port sign and a starboard sign without depending on a position of a ship. The system includes processing circuitry that acquires an image generated by a camera installed in a ship. The processing circuitry identifies whether a mode of a lateral buoy included in the image is either a first mode or a second mode. The processing circuitry determines a country to which a position of the ship detected by a position detector belongs. The processing circuitry determines whether description of a sign of the lateral buoy is the port sign or the starboard sign, from the mode of the lateral buoy and the determined country, based on a given correspondence relationship indicative of whether each of the first mode and the second mode corresponds to either one of the port sign and the starboard sign in each country.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation-in-part application of PCTInternational Application No. PCT/JP2021/042927, which was filed on Nov.24, 2021, and which claims priority to Japanese Patent Application No.JP2020-215314 filed on Dec. 24, 2020, the entire disclosures of each ofwhich are herein incorporated by reference for all purposes.

TECHNICAL FIELD

The present disclosure relates to a navigational sign identifyingdevice, an autonomous cruising system, a navigational sign identifyingmethod, and a program.

BACKGROUND ART

Patent Document 1 discloses an automatic visual recognition device whichautomatically identifies navigational signs.

REFERENCE DOCUMENT OF CONVENTIONAL ART Patent Document

-   Patent Document 1 JP-H04-076562B

DESCRIPTION OF THE DISCLOSURE Problem(s) to be Solved by the Disclosure

Meanwhile, among buoys which float on the sea surface, lateral buoysindicate either one of a port sign and a starboard sign, but theinterpretation of the port sign and the starboard sign may be oppositedepending on countries.

The present disclosure is made in view of the above-described problem,and a main purpose thereof is to provide a navigational sign identifyingdevice, an autonomous cruising system, a navigational sign identifyingmethod, and a program, which are capable of discriminating a port signand a starboard sign without depending on a position of a ship.

SUMMARY OF THE DISCLOSURE

In order to solve the above-described problem, a navigational signidentifying device according to one aspect of the present disclosureincludes an acquirer, a mode identifier, a country determinator, and aport-starboard determinator. The acquirer acquires an image generated bya camera installed in a ship. The mode identifier identifies whether amode of a lateral buoy included in the image is either one of a firstmode and a second mode. The country determinator determines a country towhich a position of the ship detected by a position detector belongs,and the position detector detects the position. The port-starboarddeterminator determines whether description of a sign of the lateralbuoy is either one of the port sign and the starboard sign from the modeof the lateral buoy and the determined country, based on a givencorrespondence relationship indicative of whether each of the first modeand the second mode corresponds to either one of the port sign and thestarboard sign in each country.

In the above-described aspect, the mode identifier may identify whethera color of the lateral buoy is either one of green and red.

In the above-described aspect, the mode identifier may identify whethera top mark of the lateral buoy is either one of a cylinder shape and acone shape.

In the above-described aspect, the navigational sign identifying devicemay further include a classification identifier which identifies aclassification of the buoy inside the image. The mode identifier mayidentify, when the classification of the buoy is a lateral buoy, themode of the lateral buoy.

In the above-described aspect, the navigational sign identifying devicemay further include a display controller which displays a symbolindicative of the description of the sign of the lateral buoy in any oneof the first image, an electronic nautical chart, and a radar image,based on the description of the sign of the lateral buoy, the positionof the lateral buoy inside the first image, and an imaging direction ofthe camera.

In the above-described aspect, the navigational sign identifying devicemay further include a consistency determinator which determinesconsistency of the description of the sign of the lateral buoy withdescription of the sign indicated by navigational sign data recorded onan electronic nautical chart, based on the description of the sign ofthe lateral buoy, the position of the lateral buoy inside the firstimage, an imaging direction of the camera, and the position of the ship.

In the above-described aspect, the navigational sign identifying devicemay further include a display controller which displays a determinationresult of the consistency in any one of the first image, the electronicnautical chart, and a radar image.

Further, an autonomous cruising system according to another aspect ofthe present disclosure may include the navigational sign identifyingdevice described above and a route calculator. The route calculatorcalculates one of a route of the ship and a width of the route based onthe position of the lateral buoy inside the first image and an imagingdirection of the camera, when the description of signs of a plurality oflateral buoys include at least two of a port sign, a starboard sign, anda safe water area sign.

Further, an autonomous cruising system according to another aspect ofthe present disclosure may include the navigational sign identifyingdevice described above, a virtual sign acquirer, and a route calculator.The virtual sign acquirer acquires data indicative of a position of avirtual sign and description of the virtual sign. The route calculatorcalculates one of a route of the ship and a width of the route based onthe description of the sign of the lateral buoy, the position of thevirtual sign, and the description of the virtual sign.

Further, an autonomous cruising system according to another aspect ofthe present disclosure may include the navigational sign identifyingdevice described above, a position detector, and a route calculator. Theposition detector detects the position of the ship. The route calculatorsets a course-changing point through which the ship is to pass based onthe description of the sign of the lateral buoy, the position of thelateral buoy inside the first image, an imaging direction of the camera,and the position of the ship.

Further, an autonomous cruising system according to another aspect ofthe present disclosure may include the navigational sign identifyingdevice described above, a direction detector, and a route calculator.The direction detector detects a heading of the ship. The routecalculator sets a direction in which the ship is to travel based on thedescription of the sign of the lateral buoy, an imaging direction of thecamera, and the heading of the ship.

In the above-described aspect, the autonomous cruising system mayfurther include an autopilot which performs an autonomous navigationcontrol based on the description of the sign of the lateral buoy.

Further, a method of identifying a navigational sign according toanother aspect of the present disclosure includes acquiring an imagegenerated by a camera installed in a ship, identifying whether a mode ofa lateral buoy included in the image is either one of a first mode and asecond mode, determining a country to which a position of the shipdetected by a position detector belongs, the position detector beingconfigured to detect the position, and determining whether descriptionof a sign of the lateral buoy is either one of a port sign and astarboard sign, from the mode of the lateral buoy and the determinedcountry, based on a given correspondence relationship indicative ofwhether each of the first mode and the second mode corresponds to eitherone of the port sign and the starboard sign in each country.

Further, a program according to another aspect of the present disclosurecauses a computer to perform processing which includes acquiring animage generated by a camera installed in a ship, identifying whether amode of a lateral buoy included in the image is either one of a firstmode and a second mode, determining a country to which a position of theship detected by a position detector belongs, the position detectorbeing configured to detect the position, and determining whetherdescription of a sign of the lateral buoy is either one of a port signand a starboard sign, from the mode of the lateral buoy and thedetermined country, based on a given correspondence relationshipindicative of whether each of the first mode and the second modecorresponds to either one of the port sign and the starboard sign ineach country.

Effect of the Disclosure

According to the present disclosure, it becomes possible to discriminatea port sign and a starboard sign without depending on the position ofthe ship.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram illustrating one example of a configuration ofa system installed in a ship.

FIG. 2 is a view illustrating description of signs of a buoy.

FIG. 3 is a block diagram illustrating one example of a functionalconfiguration of a navigational sign identifying device.

FIG. 4 is a view illustrating one example of a first image.

FIG. 5 is a view illustrating one example of identification by a firstidentifier.

FIG. 6 is a view illustrating one example of a second image.

FIG. 7 is a flowchart illustrating an example procedure of anavigational sign identifying method.

FIG. 8 is a flowchart illustrating an example procedure of a signdescription identification processing.

FIG. 9 is a view illustrating one example of a buoy management database.

FIG. 10 is a view illustrating one example of indication by a displayunit.

FIG. 11 is a view illustrating another example of indication by thedisplay unit.

FIG. 12 is a block diagram illustrating another example of theconfiguration of the navigational sign identifying device.

FIG. 13 is a block diagram illustrating still another example of theconfiguration of the navigational sign identifying device.

FIG. 14 is a block diagram illustrating one example of a configurationof a second identifier according to a first modification.

FIG. 15 is a flowchart illustrating an example procedure of aport-starboard sign identification processing.

FIG. 16 is a view illustrating one example of a by-countryport-starboard mode table.

FIG. 17 is a block diagram illustrating one example of a configurationof a second identifier according to a second modification.

FIG. 18 is a flowchart illustrating an example procedure of the signdescription identification processing.

FIG. 19 is a view illustrating lighting patterns etc. of the buoy.

MODES FOR CARRYING OUT THE DISCLOSURE

Hereinafter, one embodiment of the present disclosure is described withreference to the drawings.

FIG. 1 is a block diagram illustrating one example of a configuration ofan autonomous cruising system 100. The autonomous cruising system 100may be an ICT system mounted on a ship. Below, a ship on which theautonomous cruising system 100 is mounted is referred to as “the ship.”

The autonomous cruising system 100 may include a navigational signidentifying device 1, a camera 2, a radar 3, an MS 4, a radiocommunicator 5, a display unit 6, a GNSS receiver 7, a gyrocompass 8, anECDIS 9, and an autopilot 10. These apparatuses may be connected to anetwork N, such as a LAN, so that mutual network communications arepossible.

The navigational sign identifying device 1 may be a computer including aCPU, a RAM, a ROM, a nonvolatile memory, and an input/output interface.The CPU of the navigational sign identifying device 1 may performinformation processing according to a program loaded to the RAM from theROM or the nonvolatile memory.

The program may be supplied, for example, via an information storagemedium, such as an optical disc or a memory card, or may be supplied,for example, via a communication network, such as the Internet or LAN.

The camera 2 may be a digital camera which images outside of the ship togenerate image data. The camera 2 may be installed, for example, in abridge of the ship so as to be oriented to the bow direction of the ship(heading). The camera 2 may be a visible light camera which can image atleast a visible range. It may be capable of imaging not only the visiblerange but also an infrared range.

In this embodiment, the camera 2 may be a camera having a pan/tiltfunction and an optical zoom function (so-called “PTZ camera”). Thecamera 2 may perform pan, tilt, or zoom operation according to a commandfrom the navigational sign identifying device 1.

The radar 3 may transmit a radio wave around the ship, receive areflection wave thereof, and generate echo data based on the receptionsignal. Further, the radar 3 may discriminate or identify a targetobject from the echo data, and generate Target-object Tracking data (TTdata) indicative of a position and a speed of the target object.

The AIS (Automatic Identification System) 4 may receive AIS data fromother ships or land controls which exist around the ship. Without beinglimited to the AIS, a VDES (VHF Data Exchange System) may also be used.The AIS data may include a position and a speed of another ship.

The AIS 4 may acquire AIS data indicative of a position and descriptionof a sign of a virtual sign. The AIS 4 is one example of a virtual signacquirer. The virtual sign using the AIS is a so-called “virtual AISnavigational sign.”

The radio communicator 5 may include various radio apparatuses forrealizing communications with other ships or land controls, such asradio apparatuses of an ultrashort wave band, an intermediate wave band,and a shortwave band.

The display unit 6 may be a display device, for example, with a touchsensor (so-called “touch panel”). The display unit may be a liquidcrystal display or an organic electroluminescence display. Without beinglimited to the touch sensor, other pointing devices, such as a trackballor a mouse may also be used.

On the display unit 6, an image captured by the camera 2, a radar imagegenerated by the radar 3, an electronic nautical chart, or a syntheticimage in which the radar image is synthesized with the electronicnautical chart may be displayed.

The GNSS receiver 7 may detect the position of the ship (ship positionbased on the radio wave received from a GNSS (Global NavigationSatellite System). The GNSS receiver 7 is one example of a positiondetector which detects the ship position.

The gyrocompass 8 may detect the heading (bow direction) of the ship.The gyrocompass 8 is one example of a direction detector which detectsthe heading of the ship. Without being limited to the gyrocompass, othertypes of direction meters, such as a GPS compass, may also be used.

The ECDIS (Electronic Chart The display and Information System) 9 mayacquire the ship position from the GNSS receiver 7, and display the shipposition on the electronic nautical chart. Further, the ECDIS 9 may alsodisplay a scheduled route of the ship on the electronic nautical chart.Without being limited to the ECDIS, a GNSS plotter may also be used.

The autopilot 10 may calculate a target rudder angle for turning the bowtoward a target course based on the target course acquired from thenavigational sign identifying device 1 etc. and the heading acquiredfrom the gyrocompass 8, and drive a steering mechanism so as to bring arudder angle of the steering mechanism closer to the target rudderangle. Further, the autopilot 10 may also control an engine.

Although in this embodiment the navigational sign identifying device 1is an independent device, it may be integrated with another device, suchas the ECDIS 9. That is, the function of the navigational signidentifying device 1 may be realized by another device, such as theECDIS 9.

Further, although in this embodiment the display unit 2 is also anindependent device, without being limited to this configuration, adisplay unit provided to another device, such as the ECDIS 9, may alsobe used as the display unit 2 which displays the image generated by thenavigational sign identifying device 1.

FIG. 2 is a view illustrating the description of the signs of a buoy.The buoy may be a navigational sign which floats on the sea surface. Theclassification and the description of the sign of the buoy may beclassified according to the color of the buoy, the shape of a top mark,etc.

The classification of the buoy may include a lateral sign, a directionalsign, an isolated obstruction sign, a safe water area sign, and aspecial sign. The description of the sign of the lateral sign mayinclude a port sign and a starboard sign. The port and starboard mayindicate left and right when going to a water source. The description ofthe sign of the directional sign may include a North sign, an East sign,a South sign, and a West sign.

As for the isolated obstruction sign, the safe water area sign, and thespecial sign, the description of these signs may not be subdivided anymore, that is, it can be said that the classification of the buoy itselfindicates the description of the sign.

Meanwhile, since the buoy which floats on the sea surface is smallerthan a ship, it is difficult to identify the description of the sign ofthe buoy which is apart from the ship. Thus, in this embodiment, theaccuracy of identifying the description of the sign is improved byacquiring an image stepwise as will be described below.

FIG. 3 is a block diagram illustrating one example of a functionalconfiguration of the navigational sign identifying device 1 according toone embodiment. The navigational sign identifying device 1 may include afirst acquirer 11, a first identifier 12, a second acquirer 13, a secondidentifier 14, a display controller 15, a route calculator 16, and aconsistency determinator 18.

These function parts may be realized by the CPU of the navigational signidentifying device 1 performing information processing according to aprogram. Note that some function parts of the display controller 15 orthe route calculator 16 may be realized by a computer which is differentfrom the navigational sign identifying device 1 and included in theECDIS 9 or the autopilot 10.

Further, the navigational sign identifying device 1 may be provided witha model memory 17 which stores a learned model. This memory may beprovided to the nonvolatile memory of the navigational sign identifyingdevice 1. Without being limited to this configuration, the model memory17 may be provided outside the navigational sign identifying device 1.

The first acquirer 11 may acquire a first image generated by the camera2. In detail, the first acquirer 11 may sequentially acquire a pluralityof time-series first images generated by the camera 2, and maysequentially provide them to the first identifier 12.

The first image may be an image captured when the camera 2 is in anormal state. The normal state may be a state in which, for example, themagnification of optical zoom is the minimum, and the imaging directionis in the heading direction. The camera 2 may repeat the generation ofthe first image in the normal state, except for a period when it iscontrolled by the second acquirer 13.

For example, the plurality of time-series first images may be aplurality of still images (frames) included in a video, or may be aplurality of still images individually generated by imaging at a giveninterval.

FIG. 4 is a view illustrating one example of a first image P1 acquiredby the first acquirer 11. This drawing illustrates one example in whichthe first image P1 includes a port sign LL and a starboard sign LR whichfloat on the sea surface ahead of the ship, in addition to a ship body(hull) SP of the ship.

The first identifier 12 may identify a position of the buoy inside thefirst image P1. In detail, the first identifier 12 may identify theposition of the buoy inside the first image P1 by using a first learnedmodel stored in the model memory 17. The first identifier 12 may furtheridentify the classification of this buoy, along with the position of thebuoy inside the first image P1.

The first learned model may be generated by machine learning which usesan image for learning (learning image) as input data, and uses a labelof the buoy inside the learning image (or a label of the classificationof the buoy) and a position of the buoy as teacher data. The firstlearned model generated in this way may estimate the label of the buoyinside the first image P1 (or the label of the classification of thebuoy), the position of the buoy, and probability of the buoy. Theposition of the buoy may be expressed, for example, by coordinates of aboundary box which surrounds the buoy.

As the first learned model, an object detection model, such as an SSD(Single Shot MultiBox Detector), a YOLO (You Only Look Once), or a MaskR-CNN may be used. Without being limited to this configuration, an areadivision model, such as a Semantic Segmentation or an InstanceSegmentation, or a characteristic point detection model, such as aKeypoint Detection may be used as the first learned model.

FIG. 5 is a view illustrating one example of identification of the firstimage P1 by the first identifier 12. This drawing illustrates oneexample in which each of the port sign LL and the starboard sign LR isidentified as a buoy (or a lateral buoy), and is surrounded by aboundary box BB.

The second acquirer 13 may acquire a second image which corresponds to apartial area of the first image P1 including the position of the buoyand which is higher in resolution than the first image P1. The partialarea may be the boundary box BB (see FIG. 5 ) identified by the firstidentifier 12, for example.

The camera 2 may include a lens part 21 which realizes the optical zoomfunction, and a pan/tilt mechanism 22 which realizes the pan/tiltfunction, and the second acquirer 13 may acquire the second image bycontrolling the lens part 21 and the pan/tilt mechanism 22 of the camera2.

In detail, the second acquirer 13 may acquire the second image bycontrolling the lens part 21 so that the camera 2 magnifies a range ofthe real space corresponding to the partial area of the first image P1and images the range. Thus, by utilizing the optical zoom function, thesecond image which is higher in resolution than the first image P1 maybe acquired.

Further, the second acquirer 13 may control the pan/tilt mechanism 22 sothat the imaging direction of the camera 2 is turned to an area of thereal space corresponding to the partial area of the first image P1. Thesecond acquirer 13 may set a target value of the imaging direction ofthe camera 2 according to the position of the buoy inside the firstimage P1 identified by the first identifier 12.

FIG. 6 is a view illustrating one example of the second image P2acquired by the second acquirer 13. This drawing illustrates one examplein which the port sign LL is included in the second image P2. In thesecond image P2, it may be easier to identify the color of the port signLL and the shape of a top mark TM than in the first image P1 (see FIG. 4).

Note that, as illustrated in FIG. 5 , when a plurality of buoys (in theillustrated example, the port sign LL and the starboard sign LR) areidentified inside the first image P1, the second acquirer 13 may causethe camera 2 to sequentially image each of the plurality of buoys toacquire the second image P2 for each of the plurality of buoys.

The second identifier 14 may identify the description of the sign of thebuoy based on the second image P2. In detail, the second identifier 14may identify the description of the sign of the buoy based on the secondimage P2 by using a second learned model stored in the model memory 17.

The second learned model may be generated by machine learning in whichthe learning image is used as input data, and the label of thedescription of the sign of the buoy inside the learning image is used asteacher data. The second learned model thus generated may estimate thelabel of the description of the sign of the buoy inside the second imageP2, and the probability thereof.

As the second learned model, for example, a model similar to theabove-described first learned model may be used. In this case, the firstlearned model and the second learned model may be models in which afirst learned parameter and a second learned parameter, which aredifferent from each other, are incorporated into a common inferenceprogram.

Without being limited to this configuration, the second learned modelmay be an object identification model which identifies an object butdoes not detect the position of the object.

Further, the second learned model may include a learned model forlateral signs which is specialized in identification of the descriptionof the sign of the lateral sign, and a learned model for directionalsigns which is specialized in identification of the description of thesign of the directional sign.

FIGS. 7 and 8 are flowcharts illustrating an example procedure of anavigational sign identifying method realized by the navigational signidentifying device 1. These drawings mainly illustrate processingrelated to the acquisition of the image and the identification of thedescription of the sign among the processings performed by thenavigational sign identifying device 1.

The CPU of the navigational sign identifying device 1 may function asthe first acquirer 11, the first identifier 12, the second acquirer 13,and the second identifier 14 by performing information processingillustrated in these drawings according to the program.

As illustrated in FIG. 7 , first, the navigational sign identifyingdevice 1 may acquire the first image P1 (see FIG. 4 ) from the camera 2(S11: processing as the first acquirer 11).

Next, the navigational sign identifying device 1 may identify theposition and the classification of the buoy inside the first image P1 byusing the first learned model (S12: processing as the first identifier12).

Next, the navigational sign identifying device 1 may determine whetherthe classification of the buoy identified in the first image P1 is alateral buoy or a direction buoy (S13).

If the classification of the buoy is a lateral buoy or a direction buoy(S13→YES), the navigational sign identifying device 1 may control thecamera 2 to acquire the second image P2 (see FIG. 6 ) which is obtainedby magnifying and imaging the buoy (S14: processing as the secondacquirer 13).

Next, the navigational sign identifying device 1 may perform a signdescription identification processing for identifying the description ofthe sign of the buoy based on the second image P2 (S15: processing asthe second identifier 14).

As illustrated in FIG. 8 , at the sign description identificationprocessing S15, if the classification of the buoy is a lateral buoy(S21→lateral buoy), the navigational sign identifying device 1 mayidentify whether the description of the sign is either one of the portsign and the starboard sign, by using the learned model for lateralsigns as the second learned model (S22).

On the other hand, if the classification of the buoy is a direction buoy(S21→direction buoy), the navigational sign identifying device 1 mayidentify whether the description of the sign is either one of the Northsign, the East sign, the South sign, and the West sign, by using thelearned model for directional signs as the second learned model (S23).

Note that, if the classification of the buoy is not a lateral buoy or adirection buoy (S13→NO) (i.e., if the classification of the buoy is theisolated obstruction sign, the safe water area sign, or the specialsign), the navigational sign identifying device 1 may not acquire thesecond image P2. It is because the classification itself indicates thedescription of the sign for these buoys.

If a plurality of buoys are identified inside the first image P1 at S12,the navigational sign identifying device 1 may perform S13-S15 for allthe identified buoys (S16). That is, it may perform the acquisition ofthe second image P2 and the identification of the description of thesign for all the buoys which are the lateral buoys or the directionbuoys.

According to the above embodiment, since the description of the sign isidentified from the second image P2 which is magnified and imaged basedon the position of the buoy identified in the first image P1 and whichis higher in resolution than the first image P1, it becomes possible toimprove the accuracy of identifying the description of the sign.

Further, according to this embodiment, since the description of the signis identified from the second image P2 after the classification of thebuoy is identified in the first image P1, it can narrow down thedescription of the sign according to the classification of the buoy, andit becomes possible to further improve the accuracy of identifying thedescription of the sign.

Without being limited to this configuration, the buoy and its positionmay be identified from the first image P1, and the classification of thebuoy and the description of the sign may be identified from the secondimage P2.

FIG. 9 is a view illustrating one example of a buoy management DB(database). The buoy management DB may be a database for managing theinformation on the buoy which is identified or acquired, and may beprovided to the nonvolatile memory of the navigational sign identifyingdevice 1. The buoy management DB may include not only the information onthe buoy identified from the image of the camera 2 but also theinformation on the virtual sign acquired by the AIS 4.

The buoy management DB may include fields, such as “identifier,”“classification,” “description of sign,” “position in image,” “actualposition,” and “virtual buoy.” The “identifier” may be an identifier foridentifying the buoy. The “virtual buoy” may indicate whether it is avirtual buoy.

The “classification” may indicate the classification of the buoy. The“description of sign” may indicate the description of the sign of thebuoy. If the “classification” is a lateral sign or a directional sign,the port sign etc. or the North sign etc. may be inputted into the“description of sign.” On the other hand, if the “classification” is theisolated obstruction sign, the safe water area sign, or the specialsign, data may not be inputted into the “description of sign.”

The “position in image” may indicate the position of the buoy inside thefirst image P1 (see FIG. 4 ). Note that, in the case of the virtualbuoy, data may not be inputted into the “position in image.” The “actualposition” may indicate the actual position of the buoy. The actualposition of the buoy identified from the image of the camera 2 may becalculated based on the position of the buoy inside the image and theimaging direction of the camera 2.

Returning to description of FIG. 3 , the display controller 15 maygenerate display data related to the buoy, and output it to the displayunit 6. In detail, the display controller 15 may display a symbolindicative of the description of the sign of the buoy in the first imageP1, the electronic nautical chart, or the radar image based on thedescription of the sign of the identified buoy, the position of the buoyinside the first image P1, and the imaging direction of the camera 2.

For example, as illustrated in FIG. 10 , the display controller 15 maydisplay on the display unit 6 an image with symbols ML and MR indicativeof the description of the port sign LL and the starboard sign LR insidethe first image P1, which are associated with the positions of the portsign LL and the starboard sign LR. Each of the symbols ML and MR mayinclude a character string indicative of the description of the sign,for example.

Further, as illustrated in FIG. 11 , the display controller 15 maydisplay on the display unit 6 an image with symbols TL and TR indicativeof the description of the port sign LL and the starboard sign LR insidea synthesized image CP in which the electronic nautical chart issynthesized with the radar image, which are associated with thepositions corresponding to the actual positions of the port sign LL andthe starboard sign LR. Each of the symbols TL and TR may have a shapeindicative of the description of the sign, for example.

In the synthesized image CP, a symbol SF of the ship, a scheduled routeRT of the ship, a course-changing point DF on the scheduled route RT, asymbol EL of another ship, etc. may be displayed.

Further, symbols VL and VR indicative of the description of the virtualsigns may be displayed in the synthesized image CP. The symbols VL andVR may have similar shapes to the symbols TL and TR. Preferably, thesymbols VL and VR may be displayed so that they are discriminable fromthe symbols TL and TR, for example, by changing their transparencies.

The route calculator 16 may calculate a target course (i.e., thebearing, the course-changing point, and the route) for performing theautonomous navigation control based on the description of the sign ofthe identified buoy. The calculated target course may be provided to theautopilot 10 which performs the autonomous navigation control. Here, anincorrect recognition of the identified description of the navigationalsign may become a cause of a serious accident when performing theautonomous navigation control. Therefore, the autonomous cruising systemwhich fits for the real environment navigation can be realized byperforming the autonomous navigation control with the identification ofthe description of the navigational sign which is improved in theaccuracy by the present disclosure.

As illustrated in FIG. 5 , when the buoy identified inside the firstimage P1 includes the port sign LL and the starboard sign LR, the routecalculator 16 may calculate a scheduled route or route width of the shipbased on the positions of the port sign LL and the starboard sign LRinside the first image P1, and the imaging direction of the camera 2. Indetail, the route calculator 16 may set the scheduled route RT of theship based on the actual positions of the port sign LL and the starboardsign LR which are calculated from the positions of the port sign LL andthe starboard sign LR inside the first image P1, and the imagingdirection of the camera 2 so that the scheduled route RT passes throughbetween the port sign LL and the starboard sign LR from the shipposition (see FIG. 11 ). Without being limited to this configuration,when the buoy identified inside the first image P1 includes the portsign LL or the starboard sign LR, and the safe water area sign, theroute calculator 16 may set the scheduled route RT of the ship betweenthe port sign LL or the starboard sign LR, and the safe water area sign.

Further, the route calculator 16 may calculate a distance between theport sign LL and the starboard sign LR as a route width W based on theactual positions of the port sign LL and the starboard sign LR which arecalculated from the positions of the port sign LL and the starboard signLR inside the first image P1, and the imaging direction of the camera 2.The calculated route width W may be displayed in the first image P1displayed on the display unit 6, or may be displayed in the synthesizedimage CP in which the electronic nautical chart is synthesized with theradar image (see FIG. 11 ).

The route calculator 16 may set the course-changing point through whichthe ship goes, based on the description of the sign of the identifiedbuoy, the position of the buoy inside the first image P1, the imagingdirection of the camera 2, and the ship position. In detail, the routecalculator 16 may set one or more course-changing point DF for settingthe scheduled route RT of the ship which arrives at a port or leaves theport based on the description of the lateral sign and the sign of thedirection buoy which are identified, the actual positions of these buoyswhich are calculated from the positions of these buoys in the firstimage P1 and the imaging direction of the camera 2, and the shipposition (see FIG. 11 ). Without being limited to this configuration,the route calculator 16 may set one or more course-changing points forsetting an evading route which avoids an obstacle or a special areabased on the description of the identified isolated obstruction sign orspecial sign, the actual positions of these buoys calculated from thepositions of these buoys in the first image P1, the imaging direction ofthe camera 2, and the ship position.

The route calculator 16 may set the direction in which the ship is totravel based on the description of the sign of the identified buoy, theimaging direction of the camera 2, and the heading of the ship. Forexample, the route calculator 16 may maintain or adjust the direction inwhich the ship is to travel so that the buoy, such as the lateral buoy,continues being included in the plurality of time-series first imagesP1. Further, the route calculator 16 may set the direction in which theship is to travel by further using the position of the buoy inside thefirst image P1 so that the ship goes between the port sign and thestarboard sign, or goes in the direction along the plurality of portsigns or starboard signs.

The route calculator 16 may calculate the target course for performingthe autonomous navigation control (i.e., the direction, thecourse-changing point, and the route) based on, in addition to thedescription of the sign of the identified buoy, the position and thedescription of the virtual sign. In detail, when the data of the virtualport sign VL and the virtual starboard sign VR are acquired, the routecalculator 16 may set the scheduled route RT of the ship so that theship passes through not only between the port sign LL and the starboardsign LR which are identified inside the first image P1 but also betweenthe virtual port sign VL and the virtual starboard sign VR.

The consistency determinator 18 may determine the consistency (matching)of the description of the sign of the buoy with the description of thesign which is indicated by the navigational sign data recorded on theelectronic nautical chart based on the description of the sign of theidentified buoy, the position of the buoy inside the first image P1, theimaging direction of the camera 2, and the ship position. In detail, theconsistency determinator 18 may calculate the actual position of thebuoy based on the position of the buoy inside the first image P1, theimaging direction of the camera 2, and the ship position, and extractthe navigational sign data corresponding to the actual position of thebuoy from the navigational sign data recorded on the electronic nauticalchart, and determine whether the description of the sign of theidentified buoy matches with the description of the sign of theextracted navigational sign data.

The display controller 15 may display the determination result by theconsistency determinator 18 in the first image P1, the electronicnautical chart, or the radar image. For example, the display controller15 may display it so that a symbol indicative of “match” or “not match”is associated with the buoy in the first image P1 (see FIG. 10 ) or thesynthesized image CP (see FIG. 11 ) which are displayed on the displayunit 6. Alternatively, the display controller 15 may display the symbolindicative of the description of the sign (the symbols ML and MR of FIG.10 , or the symbols TL and TR of FIG. 11 ), for the buoy which ismatched.

The configuration of the navigational sign identifying device 1 is notlimited to the example illustrated in FIG. 3 . For example, asillustrated in FIG. 12 , the second acquirer 13A may be an imageprocessor which acquires the second image by increasing the resolutionof the partial area of the first image. Thus, by increasing theresolution, the second image which is higher in the resolution than thefirst image may be acquired.

Without being limited to this configuration, the first acquirer 11 mayacquire the first image by thinning or averaging the original imagesgenerated by the camera 2, and the second acquirer 13 may acquire thesecond image by cutting out an area corresponding to the partial area ofthe first image from the original image. The second image which ishigher in resolution than the first image may be acquired also by thisconfiguration.

Further, as illustrated in FIG. 13 , the second acquirer 13B may be acamera controller which acquires the second image by causing anauxiliary camera 3 which is higher in resolution than the camera 2 toimage an area of the real space corresponding to the partial area of thefirst image. Thus, by utilizing the auxiliary camera 3, the second imagewhich is higher in resolution than the first image may be acquired.

The auxiliary camera 3 may include, similarly to the camera 2illustrated in FIG. 3 , a lens part 31 which realizes the optical zoomfunction, and a pan/tilt mechanism 32 which realizes the pan/tiltfunction. The lens part 31 of the auxiliary camera 3 may be higher inmagnification than the lens part 21 of the camera 2.

First Modification

Below, a first modification is described. For the configuration and theprocessing which overlap with the above embodiment, detailed descriptionmay be omitted by assigning the same reference character.

The interpretation of the lateral buoy may be opposite between the portsign and the starboard sign depending on the country. Thus, in thismodification, the port sign and the starboard sign may be identified ordiscriminated without depending on the ship positioning, as describedbelow.

FIG. 14 is a block diagram illustrating one example of a configurationof a second identifier 14A according to the first modification. Thisdrawing mainly illustrates a function part for identifying thedescription of the sign of the lateral buoy, among function partsrealized by the second identifier 14A.

The second identifier 14A may include a color identifier 31, a shapeidentifier 32, a country determinator 33, and a port-starboarddeterminator 34. The color identifier 31 and the shape identifier 32 areexamples of a mode identifier.

When the classification of the buoy identified by the first identifier12 (classification identifier) illustrated in FIG. 3 is a lateral buoy,the function part of the second identifier 14A may identify thedescription of the sign of the lateral buoy included in the second imageP2 (see FIG. 6 ).

FIG. 15 is a flowchart illustrating an example procedure of aport-starboard sign identification processing S22 according to the firstmodification, which is realized by the second identifier 14A. Thenavigational sign identifying device 1 may perform the informationprocessing illustrated in this drawing according to the program.

The navigational sign identification processing S22 may correspond toS22 illustrated in FIG. 8 . That is, the navigational sign identifyingdevice 1 may perform the port-starboard sign identification processingS22, when the classification of the buoy identified at S12 illustratedin FIG. 7 is a lateral buoy.

First, the navigational sign identifying device 1 may identify whetherthe color of the lateral buoy included in the second image P2 is eithergreen or red (S31: processing as the color identifier 31). Green and redare examples of a first mode and a second mode.

Next, the navigational sign identifying device 1 may identify whetherthe top mark of the lateral buoy included in the second image P2 iseither a cylinder shape or a cone shape (S32: processing as the shapeidentifier 32). The cylinder shape and the cone shape are examples ofthe first mode and the second mode.

The identification of the color and the identification of the shape ofthe top mark may be performed using the learned model, similarly to theabove embodiment. For example, the learned model which identifies boththe color and the shape of the top mark may be used, or the learnedmodel which identifies the color, and the learned model which identifiesthe shape of the top mark may be used separately.

Next, the navigational sign identifying device 1 may determine thecountry to which the detected position of the ship detected by the GNSSreceiver 7 (see FIG. 1 ) belongs (S33: processing as the countrydeterminator 33). For example, the navigational sign identifying device1 may determine which country's territorial water the coordinates of thedetected position of the ship are included based on the nautical chartdata.

Next, the navigational sign identifying device 1 may refer to aby-country port-starboard mode table and determine whether thedescription of the sign of the lateral buoy is either the port sign orthe starboard sign based on the color identified at S31, the shape ofthe top mark identified at S32, and the country determined at S33 (S34:processing as the port-starboard determinator 34).

FIG. 16 is a view illustrating one example of the by-countryport-starboard mode table. The by-country port-starboard mode table maybe a table indicative of a correspondence relationship between the modeof the buoy and the description of the sign, and may be provided to thenonvolatile memory of the navigational sign identifying device 1.

In detail, the by-country port-starboard mode table may indicate whethergreen or red in the color of the lateral buoy corresponds to either oneof the port sign and the starboard sign in each country. Further, theby-country port-starboard mode table may indicate whether the cylindershape or the cone shape of the top mark corresponds to either one of theport sign and the starboard sign in each country.

According to the first modification described above, it becomes possibleto discriminate or identify the port sign and the starboard sign basedon the description of the sign of the lateral buoy, without depending onthe ship position.

Second Modification

Hereinafter, a second modification is described. For the configurationand the processing which overlap with the above embodiment, detaileddescription may be omitted by assigning the same reference character.

The classification of the buoy and the description of the sign may beidentifiable or discriminable based on the elements, such as the colorof the buoy, the shape of the top mark, and the lighting pattern.However, when directly identifying or discriminating the description ofthe sign based on the image, the contribution of each element may not beknown, and therefore, the identification or discrimination accuracy maynot be sufficient. Thus, in this modification, the accuracy ofidentifying the description of the sign is improved, as described below.

FIG. 17 is a block diagram illustrating one example of a configurationof a second identifier 14B according to the second modification. Thesecond identifier 14B may include a color identifier 41, a firstcandidate determinator 42, a shape identifier 43, a second candidatedeterminator 44, a lighting pattern identifier 45, a third candidatedeterminator 46, and a sign description determinator 47.

FIG. 18 is a flowchart illustrating an example procedure of a signdescription identification processing S15 according to the secondmodification, which is realized by the second identifier 14B. Thenavigational sign identifying device 1 may perform the informationprocessing illustrated in this drawing according to the program. Thesign description identification processing S15 may correspond to S15illustrated in FIG. 7 .

FIG. 19 is a view illustrating the color, the shape of the top mark, andthe lighting pattern corresponding to the description of the sign of thebuoy. The description of the sign of the buoy may be classifiedaccording to the color of the buoy, the shape of the top mark, and thelighting pattern. The lighting pattern may be a temporal pattern ofturning on and off of light.

As illustrated in FIG. 18 , the navigational sign identifying device 1may first identify a color candidate of the buoy included in the secondimage P2 (S41: processing as the color identifier 41). In detail, thenavigational sign identifying device 1 may identify the color candidateof the buoy in the second image P2 by using the learned model. Further,the navigational sign identifying device 1 may calculate a firstprobability indicative of the probability of the color candidate, alongwith the color candidate.

Next, the navigational sign identifying device 1 may determine a firstcandidate of the description of the sign of the buoy corresponding tothe identified color candidate (S42: processing as the first candidatedeterminator 42). In detail, the navigational sign identifying device 1may determine the description of the sign corresponding to the colorcandidate as the first candidate, while referring to the tableindicative of the correspondence relationship between the color and thedescription of the sign.

Next, the navigational sign identifying device 1 may identify a shapecandidate of the top mark of the buoy included in the second image P2(S43: processing as the shape identifier 43). In detail, thenavigational sign identifying device 1 may identify the shape candidateof the top mark of the buoy in the second image P2 by using the learnedmodel. Further, the navigational sign identifying device 1 may calculatea second probability which indicates the probability of the shapecandidate, along with the shape candidate.

Next, the navigational sign identifying device 1 may determine a secondcandidate of the description of the sign of the buoy corresponding tothe identified shape candidate (S44: processing as the second candidatedeterminator 44). In detail, the navigational sign identifying device 1may determine the description of the sign corresponding to the shapecandidate as the second candidate, while referring to the tableindicative of the correspondence relationship between the shape and thedescription of the sign.

Next, the navigational sign identifying device 1 may identify a lightingpattern candidate of the buoy from the plurality of time-series secondimages P2 (S45: processing as lighting pattern identifier 45). Thenavigational sign identifying device 1 may identify the lighting patterncandidate of the buoy according to a given rule.

In detail, the navigational sign identifying device 1 may extract thetemporal pattern of turning on and off of the light of the buoy from theplurality of time-series second images P2, and select a standardtemporal pattern which is most similar to the extracted temporal patternfrom a plurality of standard temporal patterns stored beforehand, as thelighting pattern candidate. The standard temporal pattern may be createdbased on the lighting pattern of the description of the sign (see FIG.19 ).

Further, the navigational sign identifying device 1 may calculate athird probability indicative of the probability of the lighting patterncandidate, along with the lighting pattern candidate. In detail, thenavigational sign identifying device 1 may calculate the similarity ofthe extracted temporal pattern to the standard temporal pattern which isthe lighting pattern candidate, as the third probability.

Next, the navigational sign identifying device 1 may determine a thirdcandidate of the description of the sign of the buoy corresponding tothe identified lighting pattern candidate (S46: processing as the thirdcandidate determinator 46). In detail, the navigational sign identifyingdevice 1 may determine the description of the sign corresponding to thestandard temporal pattern which is the lighting pattern candidate, asthe third candidate.

Next, the navigational sign identifying device 1 may determine whetherthe present time is either daytime or night (S47), and if it is daytime,it may apply a criteria for daytime (S48), and if it is night, it mayapply a criteria for night (S49). The present time may be a time atwhich the image is generated by the camera 2. The criteria may be fordetermining the description of the sign of the buoy.

Next, the navigational sign identifying device 1 may determine thedescription of the sign of the buoy based on the first candidate of thedescription of the sign determined at S42, the second candidate of thedescription of the sign determined at S44, and the third candidate ofthe description of the sign determined at S46 (S50: processing as thesign description determinator 47).

In detail, if at least two of the first candidate, the second candidate,and the third candidate are the same description of the sign, thenavigational sign identifying device 1 may determine the samedescription of the sign as the description of the sign of the buoy. Forexample, if two of the first candidate, the second candidate, and thethird candidate are the port signs, and the remaining one is thestarboard sign, the port sign may be determined as the description ofthe sign.

Further, the navigational sign identifying device 1 may determine thedescription of the sign of the buoy based on the first probability, thesecond probability, and the third probability. For example, a candidatecorresponding to the highest probability among the first probability,the second probability, and the third probability may be determined asthe description of the sign. Further, when the plurality of candidatesindicate the same description of the sign, the probability correspondingto them may be added up.

The navigational sign identifying device 1 may use different weights,which are given to the first probability, the second probability, andthe third probability daytime, respectively, between the criteria fordaytime and the criteria for night. For example, it may give priority toa candidate according to the color of the buoy and the shape of the topmark which are easily visible in a bright environment during daytime,and give priority to a candidate according to the lighting pattern ofthe buoy which is easily visible also in a dark environment duringnight.

That is, in the criteria for daytime, the weights of the first andsecond probabilities according to the color of the buoy and the shape ofthe top mark may be made higher than the weight of the third probabilityaccording to the lighting pattern of the buoy. On the contrary, in thecriteria for night, the weight of the third probability according to thelighting pattern of the buoy may be made higher than the weights of thefirst and second probabilities according to the color of the buoy andthe shape of the top mark.

Note that the technique for determining the description of the signaccording to this modification may be applied not only to the lateralsign and the directional sign but also to the isolated obstruction sign,the safe water area sign, and the special sign.

Although the embodiment of the present disclosure is described above,the present disclosure is not limited to the above embodiment, and it isneedless to say that various changes are possible for the person skilledin the art.

Terminology

It is to be understood that not necessarily all objects or advantagesmay be achieved in accordance with any particular embodiment describedherein. Thus, for example, those skilled in the art will recognize thatcertain embodiments may be configured to operate in a manner thatachieves or optimizes one advantage or group of advantages as taughtherein without necessarily achieving other objects or advantages as maybe taught or suggested herein.

All of the processes described herein may be embodied in, and fullyautomated via, software code modules executed by a computing system thatincludes one or more computers or processors. The code modules may bestored in any type of non-transitory computer-readable medium or othercomputer storage device. Some or all the methods may be embodied inspecialized computer hardware.

Many other variations than those described herein will be apparent fromthis disclosure. For example, depending on the embodiment, certain acts,events, or functions of any of the algorithms described herein can beperformed in a different sequence, can be added, merged, or left outaltogether (e.g., not all described acts or events are necessary for thepractice of the algorithms). Moreover, in certain embodiments, acts orevents can be performed concurrently, e.g., through multi-threadedprocessing, interrupt processing, or multiple processors or processorcores or on other parallel architectures, rather than sequentially. Inaddition, different tasks or processes can be performed by differentmachines and/or computing systems that can function together.

The various illustrative logical blocks and modules described inconnection with the embodiments disclosed herein can be implemented orperformed by a machine, such as a processor. A processor can be amicroprocessor, but in the alternative, the processor can be acontroller, microcontroller, or state machine, combinations of the same,or the like. A processor can include electrical circuitry configured toprocess computer-executable instructions. In another embodiment, aprocessor includes an application specific integrated circuit (ASIC), afield programmable gate array (FPGA) or other programmable device thatperforms logic operations without processing computer-executableinstructions. A processor can also be implemented as a combination ofcomputing devices, e.g., a combination of a digital signal processor(DSP) and a microprocessor, a plurality of microprocessors, one or moremicroprocessors in conjunction with a DSP core, or any other suchconfiguration. Although described herein primarily with respect todigital technology, a processor may also include primarily analogcomponents. For example, some or all of the signal processing algorithmsdescribed herein may be implemented in analog circuitry or mixed analogand digital circuitry. A computing environment can include any type ofcomputer system, including, but not limited to, a computer system basedon a microprocessor, a mainframe computer, a digital signal processor, aportable computing device, a device controller, or a computationalengine within an appliance, to name a few.

Conditional language such as, among others, “can,” “could,” “might” or“may,” unless specifically stated otherwise, are otherwise understoodwithin the context as used in general to convey that certain embodimentsinclude, while other embodiments do not include, certain features,elements and/or steps. Thus, such conditional language is not generallyintended to imply that features, elements and/or steps are in any wayrequired for one or more embodiments or that one or more embodimentsnecessarily include logic for deciding, with or without user input orprompting, whether these features, elements and/or steps are included orare to be performed in any particular embodiment.

Disjunctive language such as the phrase “at least one of X, Y, or Z,”unless specifically stated otherwise, is otherwise understood with thecontext as used in general to present that an item, term, etc., may beeither X, Y, or Z, or any combination thereof (e.g., X, Y, and/or Z).Thus, such disjunctive language is not generally intended to, and shouldnot, imply that certain embodiments require at least one of X, at leastone of Y, or at least one of Z to each be present.

Any process descriptions, elements or blocks in the flow diagramsdescribed herein and/or depicted in the attached figures should beunderstood as potentially representing modules, segments, or portions ofcode which include one or more executable instructions for implementingspecific logical functions or elements in the process. Alternateimplementations are included within the scope of the embodimentsdescribed herein in which elements or functions may be deleted, executedout of order from that shown, or discussed, including substantiallyconcurrently or in reverse order, depending on the functionalityinvolved as would be understood by those skilled in the art.

Unless otherwise explicitly stated, articles such as “a” or “an” shouldgenerally be interpreted to include one or more described items.Accordingly, phrases such as “a device configured to” are intended toinclude one or more recited devices. Such one or more recited devicescan also be collectively configured to carry out the stated recitations.For example, “a processor configured to carry out recitations A, B andC” can include a first processor configured to carry out recitation Aworking in conjunction with a second processor configured to carry outrecitations B and C. The same holds true for the use of definitearticles used to introduce embodiment recitations. In addition, even ifa specific number of an introduced embodiment recitation is explicitlyrecited, those skilled in the art will recognize that such recitationshould typically be interpreted to mean at least the recited number(e.g., the bare recitation of “two recitations,” without othermodifiers, typically means at least two recitations, or two or morerecitations).

It will be understood by those within the art that, in general, termsused herein, are generally intended as “open” terms (e.g., the term“including” should be interpreted as “including but not limited to,” theterm “having” should be interpreted as “having at least,” the term“includes” should be interpreted as “includes but is not limited to,”etc.).

For expository purposes, the term “horizontal” as used herein is definedas a plane parallel to the plane or surface of the floor of the area inwhich the system being described is used or the method being describedis performed, regardless of its orientation. The term “floor” can beinterchanged with the term “ground” or “water surface.” The term“vertical” refers to a direction perpendicular to the horizontal as justdefined. Terms such as “above,” “below,” “bottom,” “top,” “side,”“higher,” “lower,” “upper,” “over,” and “under,” are defined withrespect to the horizontal plane.

As used herein, the terms “attached,” “connected,” “mated,” and othersuch relational terms should be construed, unless otherwise noted, toinclude removable, moveable, fixed, adjustable, and/or releasableconnections or attachments. The connections/attachments can includedirect connections and/or connections having intermediate structurebetween the two components discussed.

Numbers preceded by a term such as “approximately,” “about,” and“substantially” as used herein include the recited numbers, and alsorepresent an amount close to the stated amount that still performs adesired function or achieves a desired result. For example, the terms“approximately,” “about,” and “substantially” may refer to an amountthat is within less than 10% of the stated amount. Features ofembodiments disclosed herein preceded by a term such as “approximately,”“about,” and “substantially” as used herein represent the feature withsome variability that still performs a desired function or achieves adesired result for that feature.

It should be emphasized that many variations and modifications may bemade to the above-described embodiments, the elements of which are to beunderstood as being among other acceptable examples. All suchmodifications and variations are intended to be included herein withinthe scope of this disclosure and protected by the following claims.

DESCRIPTION OF REFERENCE CHARACTERS

-   -   1 Navigational Sign Identifying Device, 2 Camera, 3 Radar, 4        AIS, 5 Radio Communicator, 6 Display Unit, 7 GNSS Receiver, 8        Gyrocompass, 9 ECDIS, 10 Autopilot, 11 First Acquirer, 12 First        Identifier, 13 Second Acquirer, 14 Second Identifier, 15 Display        Controller, 16 Route Calculator, 17 Model Memory, 21 Lens Part,        22 Pan/Tilt Mechanism, 31 Color Identifier, 32 Shape Identifier,        33 Country Determinator, 34 Port-starboard Determinator, 41        Color Identifiers, 42 First Candidate Determinator, 43 Shape        Identifier, 44 Second Candidate Determinator, 45 Lighting        Pattern Identifier, 46 Third Candidate Determinator, 47 Sign        Description Determinator, 100 Autonomous Cruising System

1. An autonomous cruising system, comprising: processing circuitryconfigured to: acquire an image generated by a camera installed in aship, identify whether a mode of a lateral buoy included in the image iseither one of a first mode and a second mode, determine a country towhich a position of the ship detected by a position detector belongs,the position detector being configured to detect the position, anddetermine whether description of a sign of the lateral buoy is eitherone of the port sign and the starboard sign from the mode of the lateralbuoy and the determined country, based on a given correspondencerelationship indicative of whether each of the first mode and the secondmode corresponds to either one of the port sign and the starboard signin each country.
 2. The autonomous cruising system of claim 1, whereinthe processing circuitry identifies whether a color of the lateral buoyis either one of green and red.
 3. The autonomous cruising system ofclaim 1, wherein the processing circuitry identifies whether a top markof the lateral buoy is either one of a cylinder shape and a cone shape.4. The autonomous cruising system of claim 2, wherein the processingcircuitry identifies whether a top mark of the lateral buoy is eitherone of a cylinder shape and a cone shape.
 5. The autonomous cruisingsystem of claim 1, wherein the processing circuitry is furtherconfigured to identify a classification of the buoy inside the image,and wherein the processing circuitry identifies, when the classificationof the buoy is a lateral buoy, the mode of the lateral buoy.
 6. Theautonomous cruising system of claim 4, wherein the processing circuitryis further configured to identify a classification of the buoy insidethe image, and wherein the processing circuitry identifies, when theclassification of the buoy is a lateral buoy, the mode of the lateralbuoy.
 7. The autonomous cruising system of claim 1, wherein theprocessing circuitry is further configured to display a symbolindicative of the description of the sign of the lateral buoy in any oneof the first image, an electronic nautical chart, and a radar image,based on the description of the sign of the lateral buoy, the positionof the lateral buoy inside the first image, and an imaging direction ofthe camera.
 8. The autonomous cruising system of claim 1, wherein theprocessing circuitry is further configured to determine consistency ofthe description of the sign of the lateral buoy with description of thesign indicated by navigational sign data recorded on an electronicnautical chart, based on the description of the sign of the lateralbuoy, the position of the lateral buoy inside the first image, animaging direction of the camera, and the position of the ship.
 9. Theautonomous cruising system of claim 8, wherein the processing circuitryis further configured to display a determination result of theconsistency in any one of the first image, the electronic nauticalchart, and a radar image.
 10. The autonomous cruising system of claim 1,wherein the processing circuitry is further configured to calculate oneof a route of the ship and a width of the route based on the position ofthe lateral buoy inside the first image and an imaging direction of thecamera, when the description of signs of a plurality of lateral buoysincludes at least two of a port sign, a starboard sign, and a safe waterarea sign.
 11. The autonomous cruising system of claim 1, wherein theprocessing circuitry is further configured to: acquire data indicativeof a position of a virtual sign and description of the virtual sign, andcalculate one of a route of the ship and a width of the route based onthe description of the sign of the lateral buoy, the position of thevirtual sign, and the description of the virtual sign.
 12. Theautonomous cruising system of claim 1, wherein the processing circuitryis further configured to: detect the position of the ship, and set acourse-changing point through which the ship is to pass based on thedescription of the sign of the lateral buoy, the position of the lateralbuoy inside the first image, an imaging direction of the camera, and theposition of the ship.
 13. The autonomous cruising system of claim 1,further comprising a direction detector configured to detect a headingof the ship, and wherein the processing circuitry is further configuredto set a direction in which the ship is to travel based on thedescription of the sign of the lateral buoy, an imaging direction of thecamera, and the heading of the ship.
 14. The autonomous cruising systemof claim 1, further comprising an autopilot configured to perform anautonomous navigation control based on the description of the sign ofthe lateral buoy.
 15. A method of identifying a navigational sign,comprising the steps of: acquiring an image generated by a camerainstalled in a ship; identifying whether a mode of a lateral buoyincluded in the image is either one of a first mode and a second mode;determining a country to which a position of the ship detected by aposition detector belongs, the position detector being configured todetect the position; and determining whether description of a sign ofthe lateral buoy is either one of a port sign and a starboard sign, fromthe mode of the lateral buoy and the determined country, based on agiven correspondence relationship indicative of whether each of thefirst mode and the second mode corresponds to either one of the portsign and the starboard sign in each country.
 16. A non-transitorycomputer-readable medium having stored thereon computer-executableinstructions which, when executed by a computer, cause the computer to:acquire an image generated by a camera installed in a ship; identifywhether a mode of a lateral buoy included in the image is either one ofa first mode and a second mode; determine a country to which a positionof the ship detected by a position detector belongs, the positiondetector being configured to detect the position; and determine whetherdescription of a sign of the lateral buoy is either one of a port signand a starboard sign, from the mode of the lateral buoy and thedetermined country, based on a given correspondence relationshipindicative of whether each of the first mode and the second modecorresponds to either one of the port sign and the starboard sign ineach country.